Calculation Methodology

This page explains the formulas, assumptions, rounding rules and limitations used in the wall putty calculators.

1. Wall area

If you know the wall area, enter it directly. Net wall area = measured surface area minus the area of doors, windows or other openings. For a rectangular room, four-wall area = 2 × (length + width) × height. If the ceiling is included, add length × width. A square metre equals approximately 10.7639104167 square feet.

2. Putty consumption

Required kg = net area (sq ft) ÷ entered coverage for two coats (sq ft/kg) × (selected coats ÷ 2) × (1 + wastage % ÷ 100). This is a linear approximation: actual consumption can change with coat thickness, surface roughness, absorbency and product formulation. Enter the relevant two-coat coverage from the product manufacturer. The default 12 sq ft/kg is a calculation example, not a universal claim.

3. Bag count and purchased material

Bags = ceiling(required kilograms ÷ bag weight in kg). The result is rounded up to whole bags. Expected unused putty = bags × pack weight − required kilograms. Material purchase cost = number of bags × price per bag. Because material is purchased in whole bags, the estimate can exceed the cost of only the exact amount consumed.

4. Labour cost and total project cost

Labour cost = net area in sq ft × entered all-coats labour rate per sq ft. The main calculator adds labour to the cost of full putty bags. The labour rate should describe the same job scope and coat count as your quote. Painting, primer, taxes, transport, repairs and special scaffolding are excluded unless included within your own entered rates.

5. Worked example

For 1,000 sq ft net wall area, two coats, 12 sq ft/kg coverage and 10% wastage: 1,000 ÷ 12 × 1.10 = 91.67 kg. For 20 kg bags, round up 91.67 ÷ 20 to 5 bags. At a hypothetical ₹850 per bag, material is ₹4,250. At a hypothetical labour rate of ₹8 per sq ft, labour is ₹8,000 and the total is ₹12,250.

Sources and product differences

JK Cement gives product-specific coverage figures in its wall putty information. Asian Paints provides technical instructions in its undercoat product guidance. These sources show why you should use the exact product sheet rather than treating one rate as applicable to every putty. We do not automatically fetch dealer prices or contractor quotes.

Validation and revisions

Calculator inputs must be finite, areas and coverage must be positive, opening area must be smaller than gross area, price and labour inputs cannot be negative, and wastage must be between 0% and 100%. We review inputs, formulas and source links when we update tools. Last methodology review: October 2026.